The crack was discovered on Oct. 14 during overflights of Pine Island Glacier as part of NASA’s Operation IceBridge, the largest airborne survey of Earth’s polar regions ever flown. The survey is presently in its third Antarctic season.

Twelve days later, researchers took advantage of a break in the weather to return to the rift, taking detailed measurements using LIDAR sensors on board NASA’s DC-8. They found that, at its widest, the rift was about 820 feet (250 meters), although for much of its 18-mile (30 km) length it averaged approximately 260 feet (80 meters). It appears to be, researchers told reporters during a conference call on Thursday, widening by roughly 2 meters (6 feet) a day. At between 165 and 195 feet (50 to 60 meters) deep, it could comfortably accommodate the Statue of Liberty. The widening crack, and the amount of ice between it and the seaward edge of the glacier, suggests the glacier will calve an iceberg approximately 340 square miles (880 square kilometers) in area, “later this year or early next year,” IceBridge project scientist Michael Studinger of NASA’s Goddard Space Flight Center said during the call.

“We are actually now witnessing how it happens and it’s very exciting for us,” Studinger observed in a press release. “It’s part of a natural process but it’s pretty exciting to be here and actually observe it while it happens. To my knowledge, no one has flown a LIDAR instrument over an actively developing rift such as this.”

As Studinger pointed out, the calving process itself is not unusual. Pine Island calves a large iceberg approximately every 10 years, and the last event was in 2001. In the long term, he told reporters, the more interesting and significant issue is not that the glacier is calving, but that it is thinning – and, said Studinger, the area that is thinning is growing.